Apparatus for electroplating apertured and irregularly shaped substrates



Jan. 28, 1969 G. FRANK 3,424,667

APPARATUS FOR CTROPLATING APERTURED AND IRREGULARLY SHAPED SUBSTRATESFiled April 5, 1966 Sheet of 5 INVENTOR.

Jan. 28, 1969 G. A. FRANK 3,424,657

APPARATUS FOR ELECTROPLATING APERTURED AND IRREGULARLY SHAPED SUBSTRATESSheet u! 5,.

Filed April b, 1966 Jan. 28, 1969 G. A. FRANK 3,424,657

APPARATUS FOR ELECTROPLATING APERTURED 7 AND IRREGULARLY SHAPEDSUBSTRATES Filed April 5, 1966 Sheet 4 of 5 United States Patent O 7Claims This invention relates to an apparatus for electroplatingapertured and irregularly shaped substrates, more particularly to anapparatus in which an electrolyte is flushed back and forth through theapertured substrate, thereby purging any gas bubbles, formed duringplating, from crevices in the substrate.

It is known in the art of electroplating that if the electrolyte is notagitated the ion density immediately surrounding the substrate becomessubstantially lower than the average ion density through the remainingelectrolyte thereby limiting the maximum current density obtainable.Therefore, it has become common practice to agitate the electrolyte atan optimum flow rate during the plating process to increase the maximumcurrent density for best plating. It is also known that gas bubbles tendto form during the plating process at the surface of the substrate beingplate. When the substrate has small apertures, crev ices, or othersurface irregularities, the bubbles tend to congregate in theseirregularities thereby further preventing uniform plating. Agitating theelectrolyte at a higher rate than that optimum for plating will causeturbulent flow and purge the bubbles from the substrate but the effectof maximum current density is lost. Existing apparatus forelectroplating employ pumps, propellers, paddlewheels and the like tocirculate or agitate the electrolyte at a flow rate which is acompromise between the optimum for plating and the optimum for purgingbubbles. Another problem exists when a substrate is to be plated on bothsides in that a flow of electrolyte in one direction over, around and/or through the substrate will improve the plating on one side but willresult in inferior plating on the other.

Therefore, it is an object of this invention to provide a new andimproved apparatus for electroplating apertured and irregularly shapedsubstrates.

An additional object of this invention resides in electroplatingapparatus wherein an electrolyte is circulated at a first rate to insuremaximum plating, and then the electrolyte is circulated at a second rateto insure maximum purging of trapped gas bubbles.

It is a further object of this invention to provide an electroplatingapparatus in which there is a novel arrangement of the component partssuch that trapped gasses upon being purged are effectively conveyed outof the solution.

It is still another object of this invention to provide an improvedapparatus for electroplating which reciprocates the electrolyte back andforth alternately at different flow rates to insure uniformed plating onboth sides of an article to be plated.

With these and other objects in view, the present invention contemplatesan electroplating apparatus in which two fluid-forcing systems cooperateto provide alternate flow at first a rate for optimum plating at a highcurrent density and then at a second rate optimized for effectivelypurging gas bubbles from surface irregularities on the substrate. Moreparticularly, a plating container is mounted on an incline andelectrodes, together with an apertured substrate, are mounted andarranged therein to provide an exit path along with trapped gas bubblesare purged and conveyed from the plating chamber.

3,424,667 Patented Jan. 28, 1969 ICC The first fluid-forcing systemincludes a pumping device for reciprocating the electrolyte back andforth past the substrate, thereby obtaining optimum plating on bothsides of the substrate and in the surface irregularities and apertures.

The second fluid-forcing system includes a ram mounted in a lowerportion of the inclined container for reciprocating between a first anda second position to force the electrolyte through the apertures in thesubstrate. On the upward stroke purged gas bubbles rise and leave thecontainer. On the downward stroke, however, the gas bubbles are forceddown into the inclined container and are trapped and congregate in aspace or pocket behind the substrate. On the next upward stroke thesetrapped bubbles are forced and conveyed along the exit path, togetherwith the bubbles purged on that stroke.

Other objects and advantages will become apparent by reference to thefollowing detailed description and drawings, wherein:

FIG. 1 shows a perspective view of a substrate susceptible of beingplated by the novel apparatus of this invention;

FIG. 2 is an assembly view partially in section, of a plating apparatuswhich embodies the principles of the invention;

FIG. 3 is a sectional view taken along line 3--3 of FIG. 2 showing therelationship of plating electrodes in an upper section of an electrolytecontainer;

FIG. 4 is -a sectional view taken along line 4-4 of FIG. 2 showing thedetail of a first anode positioned in the upper section of thecontainer; FIG. 5 is a sectional view taken along line 5- 5 of FIG. 2showing the detail of a substrate rack with the substrates to be platedmounted thereon and the position of the rack in the upper section of thecontainer;

FIG. 6 is a sectional view taken along line 6-6 of FIG. 5 showing thecross-section of the substrate rack;

FIG. 7 is a sectional view taken along line 7-7 of FIG. 2 showing thedetail of a second anode positioned in the upper section of thecontainer;

FIG. 8 is a side view of a second anode assembly showing spacers whichform an integral part thereof;

FIG. 9 is a schematic diagram of a fluid-forcing system employed in theplating process;

FIG. 10 is a diagram of a circuit for controlling the plating apparatus;and

FIG. 11 is a cam timing chart illustrating the relative times ofoperation of various circuit components illustrated in FIG. 10.

Referring now to FIG. 1, there is shown a substrate or workpiece 16 madefrom an insulating material which is susceptible of being selectivelycopper plated on both of its surfaces 17 and inside of small apertures18 therethrough by the novel apparatus of this invention. As is known inthe art, an insulator is rendered susceptible of being selectivelyelectroplated by vapor depositing a conducting material through a maskonto the areas of the insulator which are to be plated.

Considering now the plating apparatus shown in FIG. 2, a container orplating tank 19 is divided into a lower, cylindrical section 21 and anupper, rectangular section 22 by a wall 23 having a connecting orifice24 therethrou-gh. The container is mounted on an incline by a supportbase 26 secured to a leg 27.

As can best be seen in FIGS. 2 and 3, the upper section of the container22 has two runners or electrode supports 28 spaced from each other alongthe bottom of the upper section 22. Extending from opposite sides 29 ofthe upper section 22, are pairs of guide plates 31. Each guide plate 31has two holes 32 therein. These runners 28 and guide plates 31 serve tosupport a substrate rack or electrode 3 assembly 33 and a pair of anodesor electrode assemblies 34 and 36.

Referring now to FIG. 4, the first anode or electrode assembly 34 isdepicted as comprising a frame 37, which is open and generallyrectangular in shape. A plurality of copper strips 38 are secured acrossthe opening in the frame 37 by fasteners 39 in a spaced arrangement toprovide passageways 41 for the flow of an electrolyte. The copper strips38 form the active portion of the anode, serving as a source of copperions.

The substrate rack or electrode assembly 33, as shown in FIGS. 5 and 6,comprises a flat sheet-like body member 42 with four elongated slottedpassageways 43 formed by five bars 44-48. The bars 44, 46 and 48 arethicker than bars 45 and 47. Above each passageway 43 is a vent hole 49.Bars 44, 46 and 48 have grooves 51 formed on the sides which areadjacent the passageways 43. The grooves 51 are level with uppersurfaces 52 of bars 45 and 47. Clamping plates 53 having edge grooves 54are aflixed to the upper surfaces 52 of bars 45 and 47 by locking screws56. The substrate rack 33 is loaded with a plurality of substrates 16 byloosening the locking screws 56 and sliding one side of each substrate16 into one of the grooves 51 and the other side of each substrate 16into an adjacent edge groove 54. The substrates 16 are positioned sothat none of the surfaces to be plated are covered by the bars 44-48 orthe clamping plates 53 and the four vent holes 49 are not covered. Theclamping plates 53 are then tightened to secure the substrates 16 inposition.

The second anode or electrode assembly 36, see FIGS. 7 and 8, iscomposed of two plates 57 and 58. The front plate 58 is similar inconstruction to the first anode assembly 34, that is, it is open andthere are a plurality of copper strips 38 fastened across the opening.The front anode plate 58 is spaced from the solid rear plate 57 byspacers 59. As shown in FIGS. 2 and 3, a second set of spacers 61 areattached to the front of plate 58 for positioning the second anodeassembly 36 in the upper section 22 of the container 19 from thesubstrate rack 33.

As can best be seen in FIGS. 2 and 3, the three electrode assemblies 33,34 and 36 are mounted in the upper section 22 of the container 19 andrest on the runners 28 between the guide plates 31. The electrode andrack assemblies 33, 34 and 36 have handles 62, 63 and 64, respectively,for placing the assemblies on the runners 28 and between the guideplates 31. A bracket 66 is secured to a rear wall 67 of the uppersection 22. A locking member 68 is pivotally secured to the bracket 66by a pin 69. Upon placing the electrode assemblies 33, 34 and 36 in theupper section 22, the locking member 68 is pivoted to lock theassemblies 33, 34 and 36 against a face of the dividing wall 23 so thatan electrolyte flowing from the lower section 21 to the upper section 22of the container 19 will pass through the connecting orifice 24 in thedividing wall 23, the passageways 41 and the vent holes 49 provided inthe electrode assemblies 33, 34 and 36 and the apertures 18 provided inthe substrates 16.

Referring again to FIG. 2 a ram 71 is mounted in sliding engagement withthe lower section 21 of the container 19. An O-ring 72 is placed in acircumferential slot 73 formed in the periphery of ram 71, therebyproviding a dynamic fluid seal with the wall of the cylindrical section.21. The ram 71 is reciprocated between an upper position as shown inFIG. 2 and a lower position by an air cylinder 74. The ram 71 flushes anelectrolyte through the apertures 18 in the substrates 16 at a ratewhich produces turbulence, thereby purging bubbles from the apertures18. The air cylinder 74 is operated by selective actuation of normallyclosed valves 76a and 77a connected to a source of compressed air, notshown. The valves 76a and 77a, respectively, are actuated by solenoids76 and 77.

In the floor of the lower section 21 of the container 19 is a firstfluid outlet 78 adjacent to and above the face of the ram 71 where it isin the upper position. A second fluid outlet 79 is extended through abottom wall of the upper section 22 adjacent to the right hand side ofthe electrode assembly 36. A fluid-pumping system 81 is connected to thefluid outlets 78 and 79 for flushing an electrolyte back and forth pastsubstrates 16 and through the apertures 18 therein at a rate whichproduces laminar flow thereby continuously supplying ion richelectrolyte to the surface being plated.

FIG. 9 shows the details of the fluid-pumping system 81. One side of apump 82 is connected through a filter 83, a conduit 84 and a valve 86ato the second fluid outlet 79. The other side of pump 82 is connected tothe first fluid outlet 78 through a throttle valve 87, a conduit 88 anda valve 89a. The second fluid outlet 79 is also connected to the conduit88 by a valve 91a and a conduit 92. Further, the conduit 84 is alsoconnected through a conduit 93 and a valve 94a to the first fluid outlet78. A return bypass path around the throttle valve 87, the pump 82 andthe filter 83 is provided through valve 96a and conduit 97. The valves86a, 89a, 91a and 94a may be considered as being normally closed, andvalve 96a as being normally open to allow the pump 82 to continuouslyoperate to circulate a portion of the electrolyte through the bypassconduit 98. During a cycle of operation each valve 86a, 89a, 91a, 94a,and 96a, respectively, has a control solenoid 86, 89, 91, 94 and 96 tocontrol the flow of electrolyte through either the outlet 78, the outlet79 or by bypass conduit 98.

Considering now the overall operation of the apparatus with particularreference to FIGS. 2, 9 and 10, the ram 71 is initially in its upperposition. The first anode assembly 34, the substrate rack 33 loaded withsubstrates 16, and the second anode assembly 36 are mounted on therunners 28 in the upper section 22 of the container 19. The container isfilled with an appropriate electrolyte, such as a solution of a coppersalt, up to a level designated 99 in FIG. 2. A source of electricalenergy 110 is connected through leads 111 to the substrates 16 and theanodes 34 and 36.

Referring particularly to FIG. 10, the plating cycle is started byclosing a main power or start switch 112 to apply current from a source113 through normally closed contact 114-1, through a pair of timers 114and 104. A second current path is closed through start switch 112 andmotor 85, energizing motor 85 to start pump 82 pumping fluid. A thirdcurrent path is also closed through start switch 112, normally closedcontact 100-3, normally closed contact 1013 and solenoid 96 therebyenergizing solenoid 96 to open valve 96a to allow the pump 82 tocontinuously pump fluid through the return pat-h while valves 86a, 89a,91a and 94a remain in the normally closed position. The timer 104 drivesa series of four cams to control the operation of four contacts 104-1through 104-4. The action of the cams in controlling the associatedcontact closure sequence is shown in the chart in FIG. 11. The timer 104continuously cycles as long as power is applied. The timer 114 controlsnormally closed contact 114-1 to open after a predetermined intervalthereby ending the overall plating cycle by opening the current pathfrom timers 114 and 104. When the current path is broken by the openingof contact 114-1, the timer 104 is returned to its initial state openingcontacts 104-1 through 104-4.

When contact 10 41 is closed by its associated timer cam a current pathis established through start switch 112, through normally closed contact103-2 and through relay 100, energizing relay 100, thereby closingnormally opened contact 100-1 and opening normally closed contacts 100-2. The closing of relay contact 100-1 closes a current path throughstart switch 112. and solenoid 76 thereby opening normally closed valve76a, to supply compressed air to cylinder 74 which draws ram 71 to thelower position. The electrolyte following the ram flows through theapertures 18 in substrates 16 thereby purging any gas bubbles which haveformed due to the plating that has taken place thus far. These bubblesare forced down into the inclined container 19 and are trapped in apocket behind the substrate rack 33. After an interval, as shown in thetiming chart of FIG. 11 elapses, contact 104-2 is closed by itsassociated timer cam. The cam associated with contact 104-1 thenreleases contact 4-1, thereby deenergizing relay 100 by opening thecurrent path thereto, returning the contact 100-2 to its normally closedposition and returning contact 100-1 to the normally opened position.The closing of contact 100-2 closes a circuit through relay 101, throughcontact 104-2 and start switch 112. Relay 101 opens normally closedcontact 101-2 and closes normally opened contact 101-1.

The opening of contact 100-1 deenergizes solenoid 76, closing vlave 76a.The closing of contact 101-1 closes a current path through start switch112 and solenoid 77, opening valve 77a to apply compressed air from asource, not shown, to air cylinder 74, thereby returning ram 71 to itsupper position. The ram 71 pushes the electrolyte past the anodes 34 and36 and the substrates 16 and through the apertures 18 therein. Thegasses purged on the previous stroke and trapped behind the substraterack are now pushed through vent holes 49 and are expelled from theupper section 22 along with the gas purged on that stroke. Some platingdoes occur during these two portions of the cycle, however, the primepurpose for actuating the ram is to clear gas bubbles from the apertures18 in the substrates 16 to provide gas free surfaces which can beeffectively plated.

With ram 71 in its upper position, contact 104-3 is closed by itsassociated timer cam. At this time, contact 104-2 is opened by itsassociated timer cam, opening the current path through relay 101. Relay101 is deenergized thereby opening contact 101-1 and closing normallyclosed contacts 101-2. The opening of contact 101-1 opens the currentpath through solenoid 77 whereupon valve 77a is again closed. Theclosing of normally closed contact 101-2 completes a current paththrough start switch 112., contact 104-3 and relay 102. Relay 102 closescontact 102-1 and opens normally closed contacts 102-2, and 102-3. Theopening of contact 102-3 deenergizes solenoid 96 so that valve 96a isclosed to interrupt the bypass path around pump 82. The closing ofcontact 102-1 completes an energizing circuit through start switch 112and solenoids 86 and 89 which respectively opens normally closed valves86a and 89a. The opening of valves 86a and 89a provides a path for theelectrolyte to flow from pump 82 through filter 83, through conduit 84,through valve 86a, through second fluid outlet 79, past the electrodeassemblies 33, 34 and 36 and through the apertures 18 of substrates 16,through first fluid outlet 78, through valve 89a, through conduit 88,through throttle valve 87, back to pump 82. The rate of flow ofelectrolyte is optimized for best plating by controlling throttle valve87. The electrolyte flowing in the container 19 from right to leftprovides ion rich electrolyte to the surface 17 of the right hand sideof substrates 16 mounted in substrate rack 33 and to the apertures 18 insubstrates 16.

Next, the contact 104-4 is closed by its associated timer cam andcontact 104-3 is opened by its associated timer cam. The opening ofcontact 104-3 de-energizes relay 102, thereby opening contact 102-1 andclosing contacts 102-2 and 102-3. The opening of contact 102-1deenergizes solenoids 86 and 89 whereupon valves 86a and 89a are closed.The closing of contact 104-2 completes an energizing circuit throughstart switch 112, contact 104-4 and relay 103. Energized relay 103 opensnormally closed contacts 103-2 and 103-3 and closes normally openedcontact 103-1. The opening of contact 103-2 maintains solenoiddeenergized which maintains valve 96a closed, thereby maintaining thereturn path closed. The closing of normally opened contact 103-1completes an energizing circuit through start switch 112, throughsolenoids 91 and 94 which function to open valves 91a and 94a. Theopening of valves 91a and 94a provides a flow path for the electrolytefrom the pump 82, through filter 83, through conduit 93, through valve94a, through first fluid outlet 78, from left to right, through thecontainer 19, past the electrode assemblies 33, 34 and 36, throughsecond fluid outlet 79, through valve 91a, through conduit 92, throughthrottle valve 87 back to the pump 82. The rate at which pump 82operates and the setting of the throttle valve 87 are not altered,therefore, the rate of flow of electrolyte from left to right in thecontainer is the same rate for optimum plating as when the electrolytewas flowing from right to left. It is to be understood that the settingof throttle valve 87 may be cyclically varied so that the flow rate maybe at a first rate through outlet 71 and at a second rate through outlet72 to obtain maximum plating during the plating portion of the overallcycle of the apparatus. The flow from left to right provides ion richelectrolyte to the left hand surface 17 .of the substrates 16 mounted insubstrate rack 33 and the apertures 18 in substrate 16, therebyoptimally plating the substrates 16 on the left hand side and in theapertures 18. Contact 104-4 is opened by its associated timer cam andcontact 10*4-1 is again closed by its associated cam repeating the cycleas above described until timer .114 opens contact 114-1, therebycompleting the plating cycle. As can be seen in FIG. 11, the platingportion of the cycle is swbstantially longer than the portion of thecycle devoted to purging the gas.

It is to be understood that the above described arrangements ofapparatus and construction of elemental parts are simply illustrative ofan application of the principles of the invention and many othermodifications may be made without departing from the invention.

What is claimed is:

1. In an apparatus for electroplating an article having aperturestherethrough:

a tank for supporting said article immersed in in electrolyte,

a pair of anodes of plating material immersed in said tank on oppositesides of said article,

means for applying plating energy through said anodes,

said electrolyte, and said article,

means periodically operated for cyclically forcing said electrolyte backand forth through the apertures in said article at a first ratesufiicient to obtain a plating of the article, and

means rendered effective between said periodic operation of saidelectrolyte forcing means for forcing said electrolyte through saidapertures in said article at a second rate sufiicient to obtain apurging of gases generated during the plating of said article.

2. In an apparatus for electroplating metal from an electrolyte onto asubstrate susceptible of being electroplated, said substrate having twosides and one or more apertures extending from one of said sides to theother of said sides;

a container for receiving said electrolyte,

means for mounting an apertured substrate in said container,

an anode means mounted in said container adjacent said one side of saidsubstrate,

means for energizing said anode and said substrate with potentials ofopposite polarity,

a first means operable at a first rate for forcing said electrolyte pastsaid anode and through said apertures of said workpiece,

a second means operable at a second rate for forcing said electrolytepast said anode and through said apertures of said substrate, and

means for alternately operating said first and second forcing means.

3. An apparatus as set forth in claim 2 including:

a second anode means mounted adjacent said other side of said aperturedsubstrate, and

said second forcing means including facilities for reciprocating saidelectrolyte back and forth past said anodes and. through said aperturesof said substrate.

4. In an apparatus for electroplating metal from an electrolyticsolution onto a substrate susceptible of being electroplated, saidsubstrate having apertures extending therethrough;

a container for receiving a predetermined quantity of said electrolyticsolution,

a ram mounted for movement in said container to flush said electrolytefrom a first section of said container to a second section of saidcontainer,

means for mounting a substrate in said second section of said containerwith the apertures therein positioned to pass said flushed electrolyte,

an anode means mounted in said second section of said container andspaced from said substrate,

means for reciprocating said ram between a first position and a secondposition in said first section of said container, to flush electrolytethrough said apertures, and

means for energizing said substrate and anode to complete anelectroplating circuit through said electrolyte.

5. An apparatus as set forth in claim 4:

said container being mounted on an incline so that said first section islower than said second section, and said first position is lower thansaid second position,

said predetermined quantity of electrolyte being sufficient to coversaid anode and said substrate when said ram is in said second position,

a first fluid outlet in said container adjacent to and above said secondposition of said ram,

a second fluid outlet in said container above said anode and saidsubstrate,

means rendered effective following movement of said ram to said secondposition for forcing said electrolyte back and forth between said firstfluid outlet and said second fluid outlet past said anode and throughsaid apertures, and

means for alternatively operating said reciprocating means and saidforcing means.

6. An apparatus as described in claim 5, wherein said forcing meanscomprises:

a pump means having an intake port and an output port,

means including a first valve for connecting said first fluid outlet tosaid intake port of said pump means,

means including a second valve for connecting said second fluid outletto said output port of said pump means,

means including a third valve for connecting said first fluid outlet tosaid output port of said pump means,

means including a fourth valve for connecting said second fluid outletto said intake port of said pump means, and

means for alternately opening said first and second valves and saidthird and fourth valves to pump fluid back and forth between said firstfluid outlet and said second fluid outlet past said anode and throughsaid apertures.

7. In an apparatus for electroplating a metal from an electrolyte ontoboth sides of a substrate and inside apertures therethrough, saidsubstrate capable of being electroplated:

a container mounted on an incline for receiving said electrolyte,

a first anode means mounted in said container and having openings forsaid electrolyte to pass through,

a second anode means mounted in said container higher than said firstanode means, said second anode means having openings for saidelectrolyte to pass through,

means for mounting a rack to hold said apertured substrate between saidfirst and second anode means whereupon said electrolyte will passthrough said apertures, said rack having holes therethrough above thecenter of said rack for gas bubbles formed during plating to passthrough,

means for supplying energizing potential to said anodes and saidsubstrate, and

means for reciprocating said electrolyte back and forth through saidanode and said apertured substrate to purge gas formed during platingfrom said apertures and convey said purged gas through said hole and outof said container.

References Cited UNITED STATES PATENTS 686,395 11/1901 Dessolle 204-2393,216,917 11/1965 Knippers 204-146 XR FOREIGN PATENTS 400,591 10/1933Great Britain.

JOHN H. MACK, Primary Examiner.

D. R. VALENTINE, Assistant Examiner.

US. Cl. X.R.

1. IN AN APPARATUS FOR ELECTROPLATING AN ARTICLE HAVING APERTURESTHERETROUGH: A TANK FOR SUPPORTING SAID ARTICLE IMMERSED IN INELECTROLYTE, A PAIR OF ANODES OF PLATING MATERIAL IMMERSED IN SAID TANKON OPPOSITE SIDES OF SAID ARTICLE, MEANS FOR APPLYING PLATING ENERGYTHROUGH SAID ANODES, SAID ELECTROLYTE, AND SAID ARTICLE, MEANSPERIODICALLY OPERATED FOR CYCLICALLY FORCING SAID ELECTROLYTE BACK ANDFORTH THROUGH THE APERTURES IN SAID ARTICLE AT A FIRST RATE SUFFICIENTTO OBTAIN A PLATING OF THE ARTICLE, AND